High-energy-density materials based on 1-nitramino-2,4-dinitroimidazole

Article abstract of DOI:10.1039/c3ra40410b

New energetic salts based on 1-nitramino-2,4-dinitroimidazole were successfully synthesized. The salts were fully characterized by ¹H, ¹³C NMR and IR spectroscopy, differential scanning calorimetry (DSC), and elemental analyses. The salts were found to have good physical and detonation properties. The structure of guanidinium salt (3) was further confirmed by single-crystal X-ray diffraction. The densities of the energetic salts ranged between 1.70 and 1.93 g cm^-3 as measured by a gas pycnometer. The detonation pressures and velocities calculated by the EXPLO5 code ranged within 29.3-40.5 GPa and 8370-9209 m s^-1, respectively. The Royal Society of Chemistry 2013.

Full text of DOI:10.1039/c3ra40410b

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High-energy-density materials based on 1-nitramino-
2
,4-dinitroimidazole3
Cite this: RSC Advances, 2013, 3,
1
0859
c
a
a
a
ab
Jinhong Song, Kai Wang, Lixuan Liang, Chengming Bian and Zhiming Zhou*
New energetic salts based on 1-nitramino-2,4-dinitroimidazole were successfully synthesized. The salts
1
13
were fully characterized by H, C NMR and IR spectroscopy, differential scanning calorimetry (DSC), and
elemental analyses. The salts were found to have good physical and detonation properties. The structure
of guanidinium salt (3) was further confirmed by single-crystal X-ray diffraction. The densities of the
Received 1st December 2012,
Accepted 28th March 2013
23
energetic salts ranged between 1.70 and 1.93 g cm as measured by a gas pycnometer. The detonation
DOI: 10.1039/c3ra40410b
pressures and velocities calculated by the EXPLO5 code ranged within 29.3–40.5 GPa and 8370–9209 m
21
www.rsc.org/advances
s
, respectively.
8
potential highly energetic and insensitive explosives. For
Introduction
instance, paired with the same cation, most of 2,4,5-
Energetic salts have attracted considerable attention in recent
years because of their roles in the development of modern
high-energy-density materials (HEDMs). These salts possess
low vapour pressure, high heat of formation, and enhanced
thermal stability. Numerous nitrogen-containing heterocyc-
lic salts have been investigated by chemists in the USA,
Germany, and other countries. A large portion of these salts
trinitroimidazole (TNI)-based salts have higher densities and
9a,b
energy than 3,4,5-trinitropyrazole-based salts.
This char-
acteristic indicates that imidazolate salts would exhibit better
detonation properties than pyrazolate salts. The explosive
performances of trinitro-substituted imidazoles should
1
–4
9c
approach those of RDX. However, only TNI-based salts of
such type are known. Accordingly, our group is prompted to
develop new trinitro-substituted imidazole-based salts whose
energy level should be close to that of RDX or even higher.
With one C-nitro group transformed into N-nitro and one N–N
bond formed by the N-amination of the imidazole ring, the
formed 1-nitramino-2,4-dinitroimidazole (NADNI) has higher
formation heat than TNI, and may thus be a promising
energetic compound. Nitroamino imidazole-based salts are
unknown but these salts are expected to exhibit better
performances as potential explosives.
are based on nitroamino compounds, whose NHNO moiety is
2
an important ‘‘explosophore’’ that can act as a moderate acid.
5
For example, salts based on 5-nitroaminotetrazole, 3-amino-6-
6
a
6b
nitroamino-tetrazine, 4-nitroamino-1,2,4-triazole, 1-nitroa-
6
b
6c
mino-1,2,3-triazole,
3-azido-5-nitroamino-1,2,4-triazole,
6
d
nitroaminodiazido[1,3,5]triazine, and 4-nitramino-3,5-dini-
6
e
tropyrazole exhibit excellent performance in terms of impact
and friction sensitivity, as well as detonation velocity and
pressure. Some bis(heterocyclic) nitroamine energetic salts
have also been documented with impressive energetic proper-
In this paper, we report the synthesis, characterization, and
detonation performances of NADNI-based energetic salts .
1
,7a–b
ties,
tetrazolate)
nitroimino-1,2,4-triazolate)] (D = 9407 m s ), and 1,2,4,5-
tetrazino-3,6-bis(hydrazinium) 1,19-ethylenebis(oxy)-bis(5-
e.g., dihydrazinium ethylene-bridged bis(nitroimino-
7
a
21
(D
=
9478
m
s
), ammonium bis[3-(5-
1
21
7
b
21
Results and discussion
nitroimino-tetrazolate) (D = 9030 m s ).
Apart from the aforementioned heterocyclic compounds,
imidazole derivatives with more than two nitro groups are
NADNI was prepared according to literature procedures
10,11
(Scheme 1).
Reactions of the potassium salt of NADNI
with one equivalent amount of the corresponding chlorides of
ammonia, hydrazine, guanidine, aminoguanidine, diamino-
guanidine, triaminoguanidine, and 3,4,5-triamino-1,2,4-tria-
a
School of Chemical Engineering and the Environment, Beijing Institute of
Technology, Beijing, 100081, P. R. China. E-mail: zzm@bit.edu.cn; Fax: (+86)
1
0-68918982; Tel: (+86) 10-68918982
b
State Key Laboratory of Explosion Science and Technology, Beijing Institute of
Technology, Beijing, 100081, P. R. China
2
zole in H O resulted in the formation of salts 1–7 (Scheme 2).
All of the salts, which were isolated as powder materials in
c
School of Chemical Engineering and Material Science, Beijing Institute of
good yields (.90%), are nonhygroscopic and stable in air. The
Technology, Zhuhai, 519088, P. R. China. E-mail: song_jh@zhbit.com
1
13
structures of these salts were confirmed by H, C NMR and
IR spectroscopy, and elemental analysis. Additionally, the
structure of guanidinium salt (3) was further confirmed by
3
Electronic supplementary information (ESI) available: Ab initio computational
data. CCDC 885139. For ESI and crystallographic data in CIF or other electronic
format see DOI: 10.1039/c3ra40410b
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Scheme 1 Synthesis of NADNI.
1
13
21
single-crystal X-ray diffraction. The H and C NMR spectra
were recorded using d -DMSO as the locking solvent.
3190–3350 cm
are assigned to the N–H bonds of the
nitrogen-rich cations.
6
1
In the H NMR spectra, the proton signals of the anion were
observed at d 8.69 ppm, and they were shifted upfield
compared with the parent molecule (d 9.32 ppm). The NH
active proton signal of the parent molecule disappeared in the
salts spectra.
Properties of NADNI salts
The melting points (T
m d
) and decomposition temperatures (T )
of compounds 1–7 were determined by DSC at a heating rate of
2
1
1
0 uC min , respectively. As shown in Table 1, all the salts
1
3
decomposed without melting. The decomposition tempera-
tures of the NADNI salts fall within the range of 182 uC (1) to
In the C NMR spectra, two signals (d 123 and 140 ppm)
are assigned to the anion (the C4 resonance was not detected
1
(T
d
94 uC (7), which are lower than that of the neutral precursor
= 234 uC).
Density is one of the most important physical properties of
1
0,11
according to literature
). The other signals are associated
with the cations. The C5 and C2 peaks (123 and 140 ppm)
shifted upfield compared with the parent molecule (126 and
energetic compounds. According to the Kamlet–Jacobs equa-
1
42 ppm). These shifts suggest the anionic properties of
NADNI.
In the IR spectra, several main absorption bands at
approximately 3150, 1640, 1555, 1501, 1415, 1360, 1330, and
12
tions, the detonation pressure (P) depends on the square of
the density, and the detonation velocity (D) is proportional to
the density. The densities of all salts were measured with a gas
pycnometer (25 uC). As shown in Table 1, the densities of
NADNI salts range between 1.70 (6) and 1.93 g cm
2
1
23
1150 cm are attributed to the C–H, N–NO
2
and C–NO
2
bonds
(2).
of the anions. The intense absorption bands ranging within
Particularly, the densities of salts 1, 2, 4, and 6 fall within the
Scheme 2 Synthesis of NADNI-based salts.
1
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Table 1 Properties of energetic salts 1–7
a
b
c
d
f
g
h
i
j
k
l
m
n
T
m
T
d
d
mean
OB
D
f
H
cation
21
D
f
H
L
D
f
H
salt
D
(kJ kg
f
U
salt
21
P
D
T
(K)
del
V
0
Q
v
2
3
e
21
21
21
21
21
Salt
(uC) (uC) (g cm
)
(%)
IS (J) (kJ mol
)
(kJ mol
)
(kJ mol
)
)
(GPa) (m s
)
(L kg
)
(kJ kg
)
NADNI Dec 234 1.80
27.3
217.0
2.5
4
—
—
278.5
126.6
206.8
108.0
194.3
317.5
418.6
432.5
92.60
104.80
1356.6
633.4
925.9
488.1
766.8
1136.9
1406..9
1389.9
417.0
35.3
37.4
40.5
30.1
33.1
29.5
34.2
29.3
34.8
39.2
8684
5201 664
4240 722
4187 743
3746 744
3748 759
3862 782
3849 795
3881 740
4207 740
4135 733
26724
25945
26004
25179
25294
25517
25669
25364
26129
26060
1
Dec 182 1.88
Dec 183 1.93
Dec 191 1.77
Dec 188 1.82
Dec 192 1.70
Dec 193 1.80
Dec 194 1.73
Dec 230 1.82
Dec 287 1.91
624.4
770.0
575.9
660.3
769.0
871.5
877.5
—
504.9
500.3
475.1
473.1
459.3
460.0
452.2
—
8909
9209
8390
8696
8447
8920
8370
8748
9059
2
3
4
5
6
7
219.2 12
231.7 40
232.8 35
233.8 .40
234.8 15
238.5 13
221.6 7.4
221.6 7.4
RDX
HMX
—
—
357.0
a
b
c
d
e
f
Melting point. Thermal degradation temperature. Measured density. Oxygen balance. Impact sensitivity. Calculated molar heat of
g
h
i
j
formation of the cation. Calculated molar lattice energy. Calculated heat of formation for the salt. Energy of formation. Calculated
k
l
m
detonation pressure (Explo 5.05). Calculated detonation velocity (Explo 5.05). Explosion temperature. Volume of detonation products.
n
Explosion heat.
acceptable range for new high-performance energetic materi-
als (1.8–2.0 g cm ).
formation of the salts are calculated using the Born–Haber
energy cycles (Scheme 3). As shown in Table 1, all salts exhibit
2
3 1
2
1
The oxygen balance (OB) is used to indicate the degree to
which an explosive can be oxidized. The sensitivity, strength,
and brisance of an explosive all somewhat depend on the OB
and tend to approach their maximum values as the OB
approaches zero. The OBs of the NADNI salts are between
positive heats of formation and range from 108.0 kJ mol (3)
2
1
to 432.5 kJ mol (7).
The detonation pressures and velocities of the new highly
energetic salts, RDX, and HMX are calculated using the
1
7
program package EXPLO5 version 5.05. As shown in Table 1,
the calculated detonation pressures vary between 29.3 (7) and
40.5 Gpa (2), and the calculated detonation velocities are
2
38.5% (7) and 217.0% (1). Salts 1 and 3 possess better OBs
than RDX and HMX.
The impact sensitivities of the synthesized salts are
measured using a Fall Hammer on an HGZ-19Z0991 apparatus
2
1
found between 8370 (7) and 9209 m s (2). In terms of the
detonation pressure and velocity, salts 1, 2, and 6 are superior
2
1
(5.0 kg drop hammer; 30.0 mg sample). As shown in Table 1,
to RDX (8748 m s and 34.8 GPa, respectively) and NADNI
2
1
the IS ranges from 4.0 J (1) to 40 J (3 and 5), most samples are
(8684 m s and 36.3 GPa, respectively), and salt 2 is superior
2
1
less sensitive than RDX and HMX (7.4 J), and two of them are
to HMX (9059 m s and 39.2 GPa, respectively). Thus, the
salts are competitive energetic materials.
1
3
insensitive compounds.
The heat of formation is another important parameter to be
considered in the design of energetic salts. Recently, sig-
nificant progress has been made in the theoretical prediction
of the thermodynamic properties of energetic salts. The heat
of formation can be calculated for salts with good accuracy
X-Ray crystallography
The X-ray quality crystals of guanidinium salt (3) are obtained
by slow acetone evaporation at room temperature. The
structures are shown in Fig. 1 and the crystallographic data
are summarized in Table 2. Salt 3 crystallizes in monoclinic
1
4
(
including the heats of formation of cations and anion, as well
1
4d
as the lattice energy of salts). In the present study, the heat
of formation of the NADNI anions is calculated to be 7.1 kJ
mol by the Gaussian 03 (Revision D. 01) program suite
based on isodesmic reactions (Scheme 4). The values for the
1
P2 /c with four molecules in the unit cell and has a calculated
2
3
density of 1.76 g cm . The proton transfer from the NH group
of NADNI to guanidine is confirmed in Fig. 2a. The five atoms
of the imidazole ring in the NADNI anion are almost coplanar
2
1
15
2
a,b,16
cations are available in the literature.
The heats of
3
with the dihedral angle of 0u (Table S1, ESI ). The N1–N3 bond
Scheme 3 Born–Haber cycle for the formation for energetic salts.
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Scheme 4 Isodesmic reactions for calculations of heats of formation.
length (1.403 Å) is close to the N–N single bond length (1.45 Å),
and much longer than the N=N double bond length (1.25 Å),
which confirms the structure to be nitroamine rather than
nitroimine. As shown in Fig. 1b, the dashed lines indicate the
strong hydrogen bonding formed between the hydrogen atoms
(in the cation and CH group of imidazole) and oxygen atoms
(in the nitro groups of the anion). The discrete guanidinium
cation and NADNI anion are linked into a 3D network by
extensive hydrogen-bonding interactions. Bond lengths: [O1–
N4 1.2542(14); O2–N4 1.2507(14); O3–N5 1.2232(15); O4–N5
1
1
1
1
0
.2273(14); O5–N6 1.2237(14); O6–N6 1.2314(15); N1–C1
.3528(16); N1–C2 1.3721(16); N1–N3 1.4030(15); N2–C2
.3062(16); N2–C3 1.3534(17); N3–N4 1.3233(15); N5–C2
.4408(17); N6–C3 1.4351(17); N7–C4 1.3175(19); N7–H7A
.892(17); N7–H7B 0.891(18); N8–C4 1.3271(18); N8–H8A
Table 2 Crystallographic data for salt 3
Salt 3
Formula
CCDC number
4 7 9 6
C H N O
885139
277.19
0.56 6 0.29 6 0.05
Yellow platelet
Monoclinic
M
r
2
3
Crystal size [mm
Crystal colour and habit
Crystal system
]
Space group
a/Å
b/Å
c/Å
1
P2 /c
10.710 (4)
13.065 (5)
7.574 (2)
0.71073
90
97.613 (5)
90
L(Mo-Ka)[Å]
a (u)
b (u)
c (u)
3
V/Å
1050.3 (7)
4
Z
T/K
r [mg m
m/mm
153(2)
1.76
0.16
2
3
]
2
1
F
h/u
000
568
2.5 to 29.1
214 ¡ h ¡ 14
Index ranges
2
2
5096
17 ¡ k ¡ 17
10 ¡ l ¡ 10
Reflections collected
Independent reflections (Rint
Data/restraints/parameters
)
2787 (0.033)
2040/0/196
1.08
2
GOF on F
a
R
1
(I . 2s(I))
0.0347
wR
2
(I . 2d(I))
(all data)
(all data)
Largest diff. peak and hole/e Å
0.0793
0.0558
0.0729
0.28 and 20.23 e Å
R
1
Fig. 1 a) Thermal ellipsoid plot (50%) and labelling scheme for salt 3. Hydrogen
atoms are included but are unlabelled for clarity. b) Ball and stick packing
diagram of salt 3 viewed below the c axis. Dashed lines indicate strong
hydrogen bonding.
wR
2
23
23
a
2
2
2
2
2
o o c
v = 1/[s (F ) + (0.0472P) ] where P = (F + 2F )/3.
1
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The equation for the lattice potential energy, UPOT, takes the
2
3
form of eqn (3), where r
m m
is the density (g cm ), M is the
chemical formula mass of the ionic material (g), and the
2
1
21
21
21
coefficients c (kJ mol cm) and d (kJ mol ) are assigned
1
9
literature values.
POT (kJ mol ) = c (r
2
1
21
1/3
U
m
/Mm) + d
(3)
The subsequent task is the determination of the heats of
formation of the cations and anions, which is accomplished
using the isodesmic reaction method (Scheme 4). The enthalpy
of an isodesmic reaction (DH
the MP2(full)/6-311++G energy difference for the reaction and
the scaled zero-point energies (B3LYP/6-31+G ). The heats of
formation of the investigated cations and anions can then be
readily extracted.
f
u
298) is obtained by combining
*
*
*
*
The detonation pressure (P) and detonation velocity (D) are
calculated using the program package EXPLO5 version 5.05, in
which several parameters are modified. The input is made
using the sum formula, energy of formation, and experimental
densities measured by a gas pycnometer. The program is
based on the chemical equilibrium and the steady-state model
of detonation. The program uses the Becker–Kistiakowsky–
Wilson’s (BKW) equation of state (EOS) for gaseous detonation
1
9–23
products, and Cowan–Fickett’s EOS for solid carbon.
The
Fig. 2 Optimized structure and charge distribution in NADNI (a) and the anion
calculation of the equilibrium composition of the detonation
products is performed by applying the modified White,
Johnson, and Dantzig’s free energy minimization technique.
The program is designed to enable the calculation of
detonation parameters at the CJ point. The BKW equation in
the following form is used with the BKW set of parameters (a =
(
b) as found using natural bond orbital analysis (B3LYP/6-311+G(d,p)).
0
0
0
.864(19); N8–H8B 0.85(2); N9–C4 1.3221(17); N9–H9A
.858(18); N9–H9B 0.882(19); C1–C3 1.3711(18); C1–H1
.9500]. Symmetry codes: (i) x, y, z; (ii) 2x, y + 1/2, 2z + 1/2;
0
.5, b = 0.096, k = 17.56, and h = 4950) as stated below the
equations, where X is the molar fraction of ith gaseous
is the molar co-volume of the ith gaseous
(iii) 2x, 2y, 2z; (vi) x, 2y 2 1/2, z 2 1/2.
i
product, and k
i
Theoretical study
product:
Calculations were carried out by the Gaussian 03 (Revision
E.01) suite of programs. The geometric optimization of the
structures and frequency analyses were carried out by using
bx
a
1
4
i i
pV/RT = 1 + xe x = (kSX k )/[V(T + h)]
(4)
*
*
18
the B3LYP functional with the 6-31+G basis set, and single-
NBO analysis
*
*
point energies are calculated at the MP2(full)/6-311++G level.
All of the optimized structures were characterized to be true
local energy minima on the potential-energy surface without
imaginary frequencies.
To gain a better understanding of the structures of the neutral
molecule and anion of NADNI, structural optimization and
natural bond orbital (NBO) analysis were carried out by
1
5
Gaussian 03. As shown in Fig. 2a and 2b, all O atoms in
the nitro group and the N atoms (N3, N5, and N6) not in the
nitro group carry a negative charge, and the other atoms carry
a positive charge. In the anion, atom O14 of the nitroamine
group carries the most negative charge (20.525 e) and all O
atoms carry more negative charges (20.525 e 2 0.370 e) than
the corresponding O atoms (20.422 e 2 0.291 e) in the neutral
molecule, which indicates that the negative charge is
delocalized over the nitro group to a certain extent.
The charge distribution implies that the more negative O
atoms in the anion can form stronger hydrogen bonds with the
hydrogen atoms in the cation. The twisted angles between the
nitro group and the imidazole ring of the anion are also
smaller than those of the neutral molecule. These findings are
probably associated with the higher densities and impact
sensitivities of the salts than neutral NADNI.
Based on the Born–Haber energy cycle (Scheme 3), the heat
of formation of a salt can be simplified according to eqn (1),
where DH is the lattice energy of the salt.
L
DH u (ionic salt, 298 K) = DH u (cation, 298 K) + DH u (anion,
f
f
f
2
98 K) 2 DH
L
(1)
DH can be predicted by the formula suggested by Jenkins
L
1
9
et al. [eqn (2)], where UPOT is the lattice potential energy, and
+
2
n
M X p q
and n depend on the nature of the ions M and X ,
respectively. nM and nX are equal to three for monoatomic
ions, five for linear polyatomic ions, and six for nonlinear
polyatomic ions.
DH = U
+ [p(n /2 2 2) + q(n /2 2 2)]RT
(2)
L
POT
M
X
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Experimental section
Caution! Although none of the compounds described herein
have exploded or detonated in the course of this research,
these materials should be handled with extreme care using the
best safety practices.
General methods
1
13
H and C NMR spectra were recorded on a 400 MHz nuclear
magnetic resonance spectrometer operating at 400.18 and
00.63 MHz, respectively. The locking solvent is d -DMSO and
Fig. 3 Highest occupied molecular orbital (left) and lowest unoccupied
molecular orbital (right) of NADNI.
1
6
chemical shifts are reported in ppm relative to TMS. The
melting and decomposition points are recorded on a DSC at a
scan rate of 10 uC min . IR spectra were recorded using a
Bruker Alpha with a ATR-Ge device. Densities are measured at
room temperature using a Micromeritics Accupyc II1340 gas
pycnometer. Elemental analyses were obtained on an
Elementar Vario MICRO CUBE (Germany) elemental analyzer.
The highest occupied molecular orbitals (HOMOs) and
lowest unoccupied molecular orbitals (LUMOs) of the neutral
molecule and anion of NADNI are shown in Fig. 3 and 4,
respectively. In the neutral molecule, the nitro group
21
(N13O14O15) of C–NO2 occupies the HOMO and the nitro
group of the other C–NO occupies the LOMO. In the anion,
2
X-Ray crystallography
the nitramine group and a part of the imidazole ring occupy
the HOMO and LUMO. Obviously, more atoms occupy the
frontier orbitals in the anion than in the neutral molecule.
This result indicates that the anion is more reactive and easily
attacked by nucleophilic or electrophilic agents.
Crystals of guanidinium NADNI (NADNI-G) were removed from
the flask and covered with a layer of hydrocarbon oil. A
suitable crystal was selected, attached to a glass fibre, and
placed under a low-temperature nitrogen stream. Data for
NADNI-G were collected at 153(2) K using a Rigaku Saturn724
CCD diffractometer equipped with a graphite-monochroma-
tized Mo-Ka radiation (l = 0.71073 Å) using omega scans. Data
collection and reduction were performed and the unit cell was
Conclusions
2
4
In summary, new energetic materials of NADNI-based salts
were successfully synthesized and fully characterized. The salts
exhibit good physical and detonation properties, such as good
thermal stabilities, high densities, positive heats of formation,
high detonation pressures, and high detonation velocities. The
salts also have lower impact sensitivities than the parent. The
initially refined by the CrystalClear-SM Expert 2.0 r2 soft-
ware. The reflection data were also corrected for the Lp factors.
The structure was solved by direct methods and refined by the
least squares method on F2 using the SHELXTL-97 system of
2
5
programs. Structures were solved in the space group P2 /c for
1
NADNI-G by analysis of systematic absences. In this all-light-
atom structure, the value of the Flack parameter did not allow
the direction of polar axis to be determined and Friedel
reflections were then merged for the final refinement. Details
of the data collection and refinements are given in Table 2.
CCDC: 885139 (NADNI-G) contain the supplementary
crystallographic data for this paper. The data can be obtained
free of charge from The Cambridge Crystallographic Data
Centre via www.ccdc.cam.ac.uk/data_request/cif.
2
3
densities are determined to be 1.70–1.93 g cm , and the
detonation pressures and velocities are calculated to be 29.3–
2
1
4
0.5 GPa and 8370 –9209 m s , respectively. The impact
sensitivities are measured to be 4–40 J. The detonation
properties of salts 1, 2, and 6 are superior to that RDX (8748
2
1
m s and 34.8 GPa, respectively), and salt 2 is superior to
2
1
HMX (9059 m s and 39.2 GPa, respectively). Based on the
high density and good detonation properties, these salts show
a promising application in the area of HEDMs.
Reactants: imidazole, ammonium chloride, hydrazine
hydrochloride, guanidine hydrochloride (99%), aminoguani-
dine hydrochloride (98.5%), diaminoguanidine hydrochloride
(98.5%) and nitronium tetrafluoroborate (96%) were used as
received.
3,4,5-Triamino-1,2,4-triazole hydrochloride, triaminoguani-
dine hydrochloride were synthesized according to litera-
2
6,27
tures.
1-Nitramino-2,4-dinitroimidazole (NADNI)
1
-Nitramino-2,4-dinitroimidazole was synthesized according
1
0,11
1
to the literature.
acetone-d , d): 6.34 (br, 1H), 8.86 (s, 1H) ppm; H NMR (400
MHz, DMSO-d , d): 6.81 (br, 1H), 9.32 (s, 1H) ppm; C NMR
6
Pale yellow power. H NMR (400 MHz,
1
6
1
3
(
100 MHz, DMSO-d , d): 126.7, 139.4, 142.4 ppm.
6
Fig. 4 The highest occupied molecular orbital (left) and lowest unoccupied
molecular orbital (right) of NADNI-anion.
1
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General procedure for the synthesis of the salts 1–7
MHz, DMSO-d
6
, d): 123.61, 139.98, 160.54 ppm; IR (neat): n =
3
1
307, 3204, 3143, 1648, 1554, 1490, 1363, 1337, 1287, 1128,
2
To a solution of NADNI (218 mg, 1.0 mmol) in H O (2 mL) was
added anhydrous potassium carbonate (0.5 eq). The resulting
mixture was stirred at room temperature for 5 min until the
2
1
067, 1031, 988, 818, 7537, 635 cm ; elemental analysis (%)
: C 14.91, H 3.13, N 52.17; found: C14.98,
calcd for C
H 3.18, N 51.81.
4 10 12 6
H N O
2
evolving CO gas ceased. Followed by adding 1 eq ammonium
chloride, hydrazine hydrochloride, guanidine hydrochloride,
aminoguanidine hydrochloride, diaminoguanidine hydro-
chloride, triaminoguanidine hydrochloride and 3,4,5-tria-
mino-1,2,4-triazole hydrochloride, respectively. After stirring
at room temperature for 1 h, the yellow precipitate was filtered
off, and recrystallized from acetone and ether.
3
,4,5-Triamino-1,2,4-triazolium 1-nitramino-2,4-
dinitroimidazolate salt (7)
Yellow powder (326 mg, 98%); H NMR (400 MHz, DMSO-d
1
6
,
1
3
d): 5.54 (s, 2H), 6.87 (br, 4H), 8.69 (br, 1H) ppm; C NMR (100
MHz, DMSO-d , d): 123.61, 139.98, 150.25 ppm; IR (neat): n =
3
1302, 1136, 1065, 1024, 889, 819, 753, 633 cm ; elemental
analysis (%) calcd for C H N O : C 18.08, H 2.43, N 50.60;
found: C 17.96, H 2.45, N 50.05.
6
351, 3291, 3154, 3120, 1642, 1553, 1507, 1484, 1417, 1337,
2
1
Ammonium 1-nitramino-2,4-dinitroimidazolate salt (1)
1
Pale yellow powder (212 mg, 90%). H NMR (400 MHz, DMSO-
6
8 12 6
1
3
d6, d): 7.07 (s, 4H), 8.62 (s, 1H) ppm; C NMR (100 MHz,
DMSO-d , d): 123.16, 141.49 ppm; IR (neat): n = 3197, 3101,
6
1
7
1
640, 1555, 1501, 1414, 1367, 1337, 1307, 1149, 1002, 892, 820,
2
1
53, 632 cm ; elemental analysis (%) calcd for C
3 5 7 6
H N O : C
Acknowledgements
5.33, H 2.14, N 41.70; found: C 15.31, H 2.18, N 41.61.
The authors gratefully acknowledge the support of Specialized
Research Fund for the Doctor Program of Higher Education
(No. 20091101110033) and the National Natural Science Fund
Project (No. 21172020).
Hydrazinium 1-nitramino-2,4-dinitroimidazolate salt (2)
1
Yellow powder (246 mg, 98%); H NMR (400 MHz, DMSO-d
d): 7.08 (s, 4H), 8.62 (s, 1H) ppm; C NMR (100 MHz, DMSO-
6
,
1
3
d
6
, d): 132.1, 53.5 ppm; IR (neat): n = 3190, 3142, 1555, 1492,
2
1
1431, 1367, 1337, 1290, 1149, 1024, 892, 820, 753, 632 cm
;
elemental analysis (%) calcd for C
3
H
6
N
8
O
6
: C 14.42, H 2.42, N
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Yellow powder (267 mg, 96%); H NMR (400 MHz, DMSO-d
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1
Yellow powder (278 mg, 95%); H NMR (400 MHz, DMSO-d ,
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3
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57.02 ppm; IR (neat): n = 3383, 3270, 3159, 1648, 1596, 1530,
484, 1428, 1351, 1215, 1150, 988, 886, 818, 753, 634 cm
2
1
;
6
elemental analysis (%) calcd for C
4 8 10 6
H N O
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47.94; found: C16.28, H 2.78, N 47.77.
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